Save Cycles Materials as Open Shading Language file
Currently this is not possible.

Gladly Blender is OpenSource and all OSL files for OSL supported nodes can be found in the git repo https://git.blender.org/gitweb/gitweb.cgi/blender.git/tree/HEAD:/intern/cycles/kernel/shaders 

There are some nodes that are Cycles specific and will not be able to run correctly in other software packages as needed variables/context might not exists in those packages or named differently.

But it should be possible to create an overall function for your Material to simulate a Cycles material graph to a certain extend.